1. Field of Invention
The present invention relates generally to database management systems, and in particular to a federated database management system that provides users and application developers with large object processing and retrieval capabilities within an SQL-based operating environment.
2. Description of Related Art
Large-scale integrated database management systems provide an efficient, consistent, and secure means for storing and retrieving vast amounts of data. This ability to manage massive amounts of information has become a virtual necessity in business today.
At the same time, wider varieties of data are available for storage and retrieval. In particular, multimedia applications are being introduced and deployed for a wide range of business and entertainment purposes, including multimedia storage, retrieval, and content analysis. Properly managed, multimedia information technology can be used to solve a wide variety of business problems.
For example, multimedia storage and retrieval capability could be used to store check signature images in a banking system. These images may then be retrieved to verify signatures. In addition, the authenticity of the signatures could be confirmed using content-based analysis of the data to confirm that the customer's signature is genuine. However, practical limitations have stymied development of large multimedia database management systems.
Multimedia database information can be managed by ordinary relational database management systems (RDBMS), or by object-oriented database management systems (OODBMS). Each of these options present problems that have thus far stymied development.
Object-oriented database management systems are unpopular because they require a large initial capital investment and are incompatible with existing RDBMSs. Further, maintaining two separate data repositories in a RDBMS and a OODBMS is inconsistent with the database management philosophy of maintaining a secure consistent central repository for all data.
RDBMSs such as the TERADATA.RTM. system are vastly more popular than OODBMS. However, existing RDBMSs cannot effectively handle large multimedia objects. Also, although RDBMS database features and functions apply equally well to alphanumeric or multimedia data types, multimedia objects introduce new semantics problems, and require new strategies for manipulating and moving extremely large objects, which would otherwise overwhelm RDBMS computational capacity and the I/O capability of the computer implementing the RDBMS.
Another problem associated with storage and retrieval of multimedia objects relates to the transmission of data from the database management system to the client requesting the data. Real-time transmission requires expensive high-throughput communications channels. For example, for real time transmission of a 100 minute audio compact disc, a data transfer rate of at 2 Kbits/sec would be required, even if the data were compressed. A 100 minute VHS movie would require 1.5 Mbits/second. High Definition Television (HDTV) would increase this requirement to 30 Mbits/sec. Also, large data instances may cause unacceptably lengthy response times to user commands, and excessive transmission costs. Also, the object data may be highly sensitive, and best transmitted over expensive high-security communication channels.
Accordingly, there is a need to extend existing RDBMSs to efficiently manipulate and move extremely large objects, especially multimedia objects. Also, there is a need to provide for secure, economical efficient selection and transmission of large object data instances to requesting clients. The present invention satisfies this need by using an intermediate database query response comprising a data surrogate associated with large object data instances. The present invention allows the user to examine intermediate database query results using this "lightweight" data surrogate before requesting object instance data transmission. The invention also provides transmission of objects over a secondary channel which may be optionally selected to optimize transmission of large object values or maintain the security of the transmitted data.